Method of freezing foods with liquid nitrogen



METHOD OF FREEZING FOODS WITH LQUD NITROGEN Fi1ed March 9, 1964 0ct. 8, 1968 VV' E. H|RTENSTEINER 2 sheetssheet 1 METHOD OF FREEZNG FO0DS WTH LIQUID NITROGEN Oct. 8 1968 yv E. H|RTENSTEINER Filed March 9 1964 2 SheetSShee 2 7 I claim: l. Method for the preservation of a food by freezing that includes maintaining the food in contact with lic uid nitrogen in a. rSt c001ing stage, then further cling 'the food in a Second c001ing Stage by advancing the f00d through an extended path within and through an elon gated Zone leading fr0m Said stage and occupied by nitr0- gen gas vap0fized by said liquid nitrogen contact with the f00d, and circulating the gas at high velocity in repeated contact with the food passing thOugh said Zone so that heat is withdrawn from inside the food at a ratc accelerated by the vel0city of the gas contacting the f00d z Method of claim l, in Which the food in said Hrst stage is passed through a bath of liquid nitfogen in open c0mmunication with Said zone 3. Method of claim l, in Which the gas is circulated in Said Zone generany transversely 0f the path of ad- Vancement Of the food.

4' Method of claim l, in Which the gas iS given OS tive displacements at Successive cati0ns along Said path and in circulating courses of now generany transversely Of Said path' 5. Method of claim 4, in Which a HOW of gas is maintained through Said Zone in the direction Of the f00d ad- Vancement and leaves the Zone at a temperature between 0 F and 100 F Method of claim 5, in which gaS iS recirculated from a location t0ward the gas eXit end of Said zone to a lower temperature 10cation toward the inlet end thereo 7- Method of claim l, in Which the food leaving Said Zone is c00led throughout t0 a temperature below 0 F and in which the gas is discharged fr0m the Zone at a temperature below 0 F and above 100 F' 8. Method of claim 7, in Which a greater p0rtion of the t0tal Sensible heat reInoved from the food is fen0ved in said first c00ling Stage.

9. Method of claim l in Which the food is maintained in contact with liquid nitrogen in said Hrst c00ing Stage for a period under one minute and then is maintained in contact with said circulating gas for a eri0d betvveen about 3 and 8 minutes 10. The method of claim 1 as applied to food products subject to Surface cracking by reason 0f the nrst Stage cooling, and in Which an aque0[1s Surface coating is aplied t0 the f00d pri0r t0 its contact With the liquid nitr0gen in the first Stage t0 prevent said cracking' ll The method of claim l, in Which the food after c00ling in Said second stage is given a coating vvhich thereafter inhibits 0Xidation Of the food' 12. The method of claim z as applied to fruits and vegetables subject to surface Cracking by reason 0f the flst stage c00ing in vhich an aqueous coating is applied t0 the food prior t0 itS contact with the li(1uid nitrogen in the first Stage to prevent Said cracking, and in Which the food after Said Second Stage c00ling iS given a coating yvhich thereafter inhibits 0Xidation of the f00d l3( The method of claim l, in which the f00d af[er c00ling in the Second Stage is sealed in packages f[0m which air has been displaced 14. The method of claim ll, in which the food after cooling in the Second stage iS Sealed in packages from which air has been displaced 15. The method of c]aim lz in which the f00d after c00ling in the second Stage iS Sealed in packages fron Which ail has been displaced.

l(;' Method for the preservation of a food by freezing, that includes advancing the food in an extended path within an elongated Zone, releasing into Said Zone nitr0- gen gas being evolved fr0In liquid nitrogen at a tenperature Of about 3Z0 F., 0Sitively displacing the gas at Successive l0cations along said path to circulate the gas generally transversey Of Said path against the f00d and at Said locations vhile passing the gas through the Zone in the directi()n of the food advancenent, and abs0rbing heat fr0m the f00d int0 the gas S0 that the temperature Of the gaS leaving Said Zone iS bel0w 0 F. and above F' 17. The method 0f claim l6, in vvhich lic llid nitrogen is introduced to Said Zone l8 I"Iethod f0r the preservation of a food by freezing, that includes c0ntinuously advancing the food in an eX tended path through and out of an elongated Zone, feeding into Said Zone nitrogen gas being evolved from liquid nitrogen at a temperature Of about -320 F-, p0sitively displacing the gas at each of Successive I0cations along Said path t0 recirculate the gaS generany transversely of Said path and against the food at each of Said 10cations, maintaining a constant Ow Of the gas through the Zone, Teleasing the gas therefr0m at a rate in c0rresp0ndence with the rate Of nitrogen introduction theret0, and ab- Sorbing heat fr()T1 the f00d into the gaS S0 that the temperature of the gas released from said Zone is bel0vv 0 F' and above l00 F.

19. The Inethod of claim 18 in vvhich liquid nitr0gen is introduced t0 Said zone 20, The method of claim 18 )in which the gas nows through the Zone in the direction of the food advancement References cited UNITED STATES PATENTS 2,38,140 9/194 Knowles 62l73 3 039 Z76 6/l962 Morrison 99193 3,2SO,630 j/1966 vvebster et al 99l93 3 Z94 j3 lz/1966 Benson 99193 3 297 4j4 1/1967 vvebster et al. 99l93 0THER REFERENCES Iressler et al.; The 1 reezing Preservation of F00d, AVI Pub C0., 197, ppll9l28.

A LOUIS MONACELL, Prm EX......m:

S. B. DAVIS, EX...er 

